8051片内有4kB的程序存储单元，其地址为0000H—0FFFH，单片机启动复位后，程序计数器的内容为0000H，所以系统将从0000H单元开始执行程序。但在程序存储中有些特殊的单元，这在使用中应加以注意：



其中一组特殊是0000H—0002H单元，系统复位后，PC为0000H，单片机从0000H单元开始执行程序，如果程序不是从0000H单元开始，则应在这三个单元中存放一条无条件转移指令，让CPU直接去执行用户指定的程序。

-8051 4kB of procedures within the storage unit, its address is 0000H-0FFFH, the microcontroller starts after reset, the program counter to 0000H, 0000H unit so the system will start the program. But in some special program stored in the unit, which in use should be noted: one group special is 0000H-0002H unit, system reset, PC for the 0000H, 0000H microcontroller unit started from the program if the program is not a location 0000H began, the three units should be stored in an unconditional branch instruction, the CPU directly to the implementation of user-specified programs.